Televisions enable us to see things occur almost the moment ____.
A.when they are happening
B.they are happening
D.they have happened（答案）
C.which they happen
此题实际考查时态。在时间从句中，用一般现在时表示将来发生的动作，用现在完成时表示将来业已完成的动作，故选择完成时。本句也可使用一般现在时。
the moment = as soon as，原句可以说：
Televisions enable us to see things occur almost as soon as hey have happened.
